Just two days after Pakistanis were jolted by a deadly terrorist attack on the country's busiest airport, militants again opened fire on security forces at Karachi's international airport.

Pakistani police and soldiers quickly repelled the assault on Tuesday (local time), and there were no reported injuries. But the incident forced the closure of Jinnah International Airport for the second time in two days and highlighted the threat posed by the Pakistani Taliban.

The clash appeared to push the country closer to a major conflict with the radical Islamist group. On Tuesday morning, the Pakistani military announced that it had carried out airstrikes against Taliban strongholds in northwestern Pakistan. An army official said 25 militants were killed.

Interior Minister Chaudhry Nisar Ali Khan warned that the airstrikes could lead to retaliation from the Pakistani Taliban.

"We need to face and acknowledge the facts: The country is in a warlike situation, and we are in a conflict zone," Khan told the National Assembly.

The latest attack began when three to four militants opened fire on a Karachi Airport Security Force base next to the airport at about noon, officials said. Pakistani news channels aired live footage of the ensuing gun battle. Officials said the militants escaped on motorcycles, and the airport resumed flights about 2.30pm.

The Pakistani Taliban asserted responsibility for Tuesday's attack.

The group launched an assault late on Sunday on the airport that left 36 people dead, including a dozen airport security personnel, four employees of Pakistani International Airlines and all 10 attackers. No passengers died.

The death toll includes seven bodies that were discovered early Tuesday in a warehouse.

Relatives of those victims had told police Monday evening that they had become trapped in a cold-storage facility while seeking refuge during the previous night's attack.

But Abid Kaimkhani, a spokesman for Pakistan's Civil Aviation Authority, said the bodies were found in a room next to the cold-storage area. They were apparently killed in a fire that swept through the building during the attack, he added.

Interior Minister Khan joined Prime Minister Nawaz Sharif and Pakistan's military chief, General Raheel Sharif, at a national security meeting on Tuesday to discuss the growing terrorism threat. Some analysts saw the gathering as a possible precursor to a broader military campaign against the Pakistani Taliban, also known as Tehrik-e-Taliban Pakistan.

Tuesday's attack appeared to originate from a slum that surrounds the airport. It was the same area that the militants used to gain entry to airport grounds Sunday night. The back-to-back incidents are raising serious concerns about the safety of commercial flights at the airport, which serves a city of 22 million residents.

Major General Asim Saleem Bajwa, a spokesman for Pakistan's security forces, noted that the assailants on Tuesday were repelled by those security forces. "No breach of [airport] fence, no entry," Bajwa said in a statement.

But Rao Anwar, a senior police official in Karachi, said: "We need to clear terrorists from these poor localities, and police will be doing that job," he said.

The Pakistani Taliban claims to be independent of the Afghan Taliban. But the groups are believed to coordinate activities.Authorities tightened security at other airports in Pakistan. Sohail Raheem, an airport security official in Peshawar in northwestern Pakistan, said three concrete walls are being built around the runway there.